'hdmx' table is used only with fonts intended for use
on the Macintosh platform. If this table is present in a font, the values
in contains will be used where appropriate. If this table is missing, the
values in the
'hmtx' table will be scaled and rounded. Using
this table will improve performance at the sizes for which it contains metric
information because it allows the Macintosh Font Manager to build integer
width tables without calling the scaler for each glyph.
The horizontal device metrics table stores integer advance widths scaled
to particular pixel per em sizes. Typically, the
is used only for selected screen sizes.
Device records in this table are sorted by pixel per em size. The checksum for this table includes all device records. Note that each device record subtable is padded with zeros to make it long aligned.
Table 20: The
|int16||format version number|
|int16||number of device records|
|int32||size of a device record, long aligned|
|DeviceRecord||records[number of device records]|
Each device record for format 0 has the structure shown in Table 21.
Table 21: Device Record
|uint8||pixel size for following widths|
|uint8||widths[number of glyphs]|
[Table of Contents]